Heat
shock protein 90 (Hsp90) inhibitors play a remarkable role
in cellular growth, and they were shown to exhibit antitumor activity.
The Hsp90 inhibitor AT13387 (onalespib) is under clinical trials for
the treatment of refractory gastrointestinal stromal tumors. Recently,
it was demonstrated that this compound also exhibits inhibition against
bladder cancer. Here, we report isoindoline- and isoindolinone-based
(halomethyl)­benzenes via a [2 + 2 + 2] cyclotrimerization in the presence
of catalytic amounts of Mo­(CO)<sub>6</sub>. This strategy has been
extended to synthesize the key precursor of the Hsp90 inhibitor, AT13387.